Source: The Fish Site
PORTUGAL – Trawling’s impacts on marine ecosystems can be assessed using simple metrics which characterise easy-to-obtain samples of fish, new research suggests. The Portuguese study shows that groups of fish become dominated by fewer species as fishing intensity increases, while their total biomass declines. Moreover, in the most fished areas there were other noteworthy changes, such as substantial reductions in the proportion of sharks and rays. Bottom trawling, a form of fishing which involves dragging nets along the seafloor, can have devastating effects on marine life. The heavy equipment used to hold the net open can damage habitats, changing the structure and function of these sensitive environments.
The EU’s Marine Strategy Framework Directive was established to protect Europe’s marine environment, addressing all human activities that have an impact on the marine environment while supporting the sustainable use of the goods and services it provides. It places ecosystems at the centre of management decisions and requires Member States to implement measures to achieve or maintain ‘good environmental status’ by 2020.
This study looked at how groups of fish can be used to indicate the ecological impacts of bottom trawling. The researchers undertook 30-minute trawls at 97 sites of soft-bottomed habitat along the Portuguese coast between 2006 and 2010. They then characterised the groups of fish they caught using 24 metrics which may be useful as indicators of environmental status as defined by the Directive. These included total biomass and the proportion of different types of species found in each sample haul.